We have observed that different approaches work faster for different configurations.
Some boards solved faster when the states stored bevor the states were visit in the "know states" list and some boards solved faster when the states stored after the the state were visit. A lot of ideas solved only faster on several boards but not generally like e.g. to backtrack in the searchtree if a box couldn't move since a specified depth. In lack of the time we weren't able to investigate every idea detailed enough. Another future idea is to join the lists of the "know states" list of the forward and reversed solvers to find a faster solution.